Multi-beam laser scanner

ABSTRACT

A laser scanner has multiple measuring beams for optical surveying of an environment. The laser scanner is configured to provide scanning with at least two different multi-beam scan patterns. Each multi-beam scan pattern is individually activatable by a computing unit of the laser scanner.

FIELD

The disclosure relates to a laser scanner having multiple measuringbeams.

BACKGROUND

To detect objects or surfaces in an environment, often methods are usedwhich perform scanning by means of a laser scanner. In this case, thespatial position of a surface point is detected in each case bymeasuring the distance to the targeted surface point by the laserdistance measuring beam and by linking this measurement to angleinformation of the laser emission. From this distance and angleinformation, the spatial position of the detected point can bedetermined and, for example, a surface can be continuously measured.Often, e.g. in parallel to this purely geometric detection of thesurface, an image recording by a camera is carried out which alsocontains further information in addition to the overall visual view,e.g. with respect to the surface texture.

3D scanning is an effective technology to produce within minutes orseconds millions of individual measurement data points, in particular 3Dcoordinates. Some measurement tasks include the recording of objects ortheir surfaces such as industrial plants, facades of houses or historicbuildings, or accident locations and crime scenes. Scanning devices withscanning functionality are, for example, total stations or theodoliteswhich are used to measure or create 3D coordinates of surfaces. For thispurpose, they may be able to guide the measuring beam—usually a laserbeam—of a distance measuring device over a surface or along an edge, andthus—at a given sampling or measuring rate—to successively capturescanning data, e.g., distance and direction, associated to differentmeasuring points.

Scanning data are referenced to each other with respect to a measuringreference point, e.g. the location or zero point of the measuringdevice, in order that they lie in a common reference or coordinatesystem. A so-called 3D point cloud can then be generated from theplurality of scanned points, e.g., from the distance measurement valueand the measuring direction correlated therewith for each point, e.g. bymeans of an integrated or external data processing system.

Measuring devices with scanning functionality may also be implemented asLiDAR systems, e.g. for airborne landscape surveying. Thereby, laserpulses are transmitted from a moving carrier, e.g. an aircraft or adrone (UAV, “unmanned aerial vehicle”), towards the surface according toa defined scanning pattern, e.g. via a rapidly adjustable deflectingelement such as a sweeping mirror or a refractive optical component.Based on returning parts of the radiation emitted to the ground anaccurate surface model of the ground to be measured can be derived, e.g.wherein the proper motion of the carrier is taken into account by meansof a global satellite positioning system (GNSS) and/or by means of aninertial measuring system (IMU).

A further measuring task for scanning measuring devices is themonitoring of an environment, e.g. within the framework of a warning orcontrol system for an industrial production facility, or in a drivingassistance system such as a collision avoidance system.

Applications of scanning instruments may also lie in undergroundconstruction or mining, e.g. in the determination of the shape and areaof tunnel cross sections or in the determination of the volume ofexcavation pits or gravel heaps.

In the area of autonomous driving vehicles, the roads to be driven maybe recorded in advance and stored in a model. For this purpose, vehiclesequipped with scanners are used to scan and map the region in question.For example, a LiDAR module may be used, which has to fulfil specializedrequirements for this task, in particular with respect to the field ofview (FoV) and the detection rate. For example, the horizontal field ofview should be about 80 degrees, wherein the vertical field of view maybe substantially smaller, e.g. about 25 degrees. The acquisition ratefor the scanning of the complete field of view is, for example,approximately 25 Hz.

In principle, such laser scanning devices are designed, for example,with an electro-optical laser-based distance meter to detect a distanceto an object point as a measuring point, wherein a deflection elementmay be present to vary the measuring direction of the laser distancemeasuring beam, e.g. with respect to one or several independent spatialdirections, whereby a spatial measuring or scanning area can becaptured.

By way of example, a deflecting unit may be realized in the form of amoving mirror or alternatively also by other elements suitable for thecontrolled angular deflection of optical radiation, such as rotatableprisms, moving optical fibers, refractive optical elements, deformableoptical components, etc. The measurement usually takes place with thedetermination of distance and angles, which is to say in sphericalcoordinates, which can also be transformed into Cartesian coordinatesfor display and further processing.

In particular, a laser scanner can have separate beam paths, e.g., onefor the transmitted radiation and one for the receiving beam, or thebeam paths of the transmitting channel and of the receiving channel canat least partially overlap. In particular, the beam paths can thus beconfigured in such a way that a deflection unit acts only on thetransmitted radiation, e.g., wherein the imaging effect of the receptionchannel is substantially independent of the control of a beam deflectingelement of the deflecting unit. By way of another example, thetransmission channel and the reception channel may each have their owndeflection unit which can be controlled separately, or a singledeflecting unit may act both on the transmitted radiation and on thereceiving radiation.

Various principles and methods may be available in the field ofelectronic or electro-optical distance measurement. One approach is toemit pulsed electro-magnetic radiation, e.g. laser light, to a target tobe measured and to subsequently receive an echo from this target as aback-scattering object, wherein the distance to the target to bemeasured can be determined by the time-of-flight (ToF), the shape,and/or the phase of the pulse. Such laser distance meters have nowbecome standard solutions in many areas.

For the detection of the returning pulse or a returning pulse sequence,two different approaches or a combination thereof are usually used.

In the so-called threshold method, a light pulse is detected when theintensity of the radiation incident on a detector of the distancemeasuring device exceeds a certain threshold value. This thresholdreduces noise and interference signals from the background beingconfused as measuring signal. However, in the case of weak returnpulses, e.g. caused by larger measuring distances, detection ofmeasuring signals is no longer possible as soon as the pulse intensityis below the set detection threshold. Thus, the essential disadvantageof this threshold method is that the amplitude of the measurement signalmay be sufficiently larger than the amplitude of optical and electricalnoise sources in the signal path. Therefore, to sufficiently reducemisdetections, a threshold may be set to a certain level whereforemeasurements over relatively long distances the threshold value methodmay only be applicable at certain conditions.

The other approach is based on sampling the returning pulse. Thisapproach may be used for weak backscattered signals (e.g. pulsesignals), e.g. caused by larger measurement distances. This method mayalso be regarded as holistic signal acquisition, wherein the completemeasuring signal as well as the essential noise information isdetermined, which leads to an increase in measuring accuracy. An emittedsignal is detected by sampling detector data associated to radiationdetected by a detector, identifying a signal within the sampled data,and finally by determining a return time of the signal. By using amultiplicity of sampling values and/or by synchronized summation of thedetector data with respect to the emission rate, a useful signal canalso be identified under unfavorable circumstances, so that measuringover even greater distances or noisy or interference-prone backgroundscenarios becomes possible.

A multi-beam laser scanner may be embodied to generate multipleindividual measuring beams, each beam having a small divergence angle,instead of a single measuring beam. Individual beams may be sent out asan initially immediately diverging or as an immediately converging setof beams, e.g. arranged in a common plane (diverging line laser/striplaser/fan laser) or arranged such that they generate a cone ofindividual beams. Alternatively, individual beams may be sent outparallel to each other.

Thus, the beams of the plurality of measuring beams are generated insuch a way that they define a plurality of substantially instantaneousscanning axes. In other words, individual pulses of different beams aregenerated “substantially at the same time”, e.g., in a time synchronizedfashion but not necessarily exactly at the same time. In some cases, theindividual pulses are sent out slightly offset to pulses of neighboringbeams, e.g. to reduce cross-talk effects.

Multi-beam laser scanners have several advantages, e.g. achieving ahigher point rate or a higher point density, e.g. with a slower rotationspeed of a rotating beam deflection mirror. However, individuallyemitted beams have to be aligned in each case to associated receptionareas, wherein crosstalk between individual beams, e.g. wherein aspecific reception area associated to a first beam detects light of asecond beam sent out close to the first beam, may limit the capabilityof multi-beam measurements.

Crosstalk limits the effective range of the multi-beam receiver. Toreduce crosstalk, several options may be available, e.g. reduction ofbeam density, beam masking using for instance LCDs, or complicatedoptical arrangements to precisely align multiple emitter-detectorpairings.

Furthermore, the point density of the measuring beams projected onto atarget object may depend on the distance between the laser scanner andthe object, wherein the point distribution may depend on an orientationof the laser scanner, particularly a relative orientation of adeflecting element with respect to a multi-beam pattern generatedupstream of the deflecting element.

For example, in the case of a line scanner an orientation of theprojected line on the object may change with the azimuth angle of arotating deflection mirror, or, by way of another example, having a setof beams diverging from a single point of origin, e.g. a cone of beams,and using only a single scan direction, e.g. defined by a rotatingmirror, the spatial resolution of the system is limited because of thehigh density of points generated in the scan direction but the lowdensity of points perpendicular to the scan direction.

It is therefore an object of the present disclosure to provide animproved and versatile laser scanner, which overcomes the abovementioned limitations.

This object is achieved by realizing the features of the independentclaim. Features which further develop the disclosure in an alternativeor advantageous manner are described in the dependent patent claims.

The disclosure relates to a laser scanner for optical surveying of anenvironment, comprising a multibeam transmitter configured forgenerating multiple measuring beams, particularly pulsed laser beams,defining multiple substantially instantaneous scanning axes, a receiverconfigured to detect returning parts of the multiple measuring beams,and a computing unit configured for controlling the laser scanner toprovide scanning of the environment by the multiple measuring beams, forderiving distance measuring data based on the multiple measuring beams,and for deriving angle data for respective emitting directions ofindividual measuring beams of the multiple measuring beams.

According to the disclosure, the laser scanner is configured to providescanning with at least two different multi-beam scan patterns, based onthe multiple measuring beams, wherein each multi-beam scan pattern isindividually activatable by the computing unit.

In particular, the multi-beam scan patterns differ from each other inthat, compared to each other, they provide at least one of a differentnumber of beams, a different projected beam density, e.g., the beamdensity projected onto a target object in the environment to be scanned,a different projected beam distribution, e.g., the beam distributionprojected onto a target object in the environment to be scanned, adifferent beam spacing, a different emission timing, particularly adifferent pulse emission timing, different individual beam shapes,particularly different divergence angles of individual beams, and adifferent spreading direction of their beams, particularly wherein onemulti-beam scan pattern is provided as a set of beams which converge toeach other such that the beams have a common point of intersection inpropagation direction of the beams, and another multi-beam scan patternis provided as a set of beams which diverge from each other.

Thus, the inventive laser scanner can be adapted on the fly to be usedin a diversity of different applications and environments, whereinoptimized workflows are enabled. For example, in the case that noa-priori knowledge of the environment or the positioning of the laserscanner is available, e.g., spatial position and/or orientation of thelaser scanner, a measuring process is enabled comprising a rough initialscan with a subsequent measuring scan, optimized based on the initialscan. With a-priori knowledge of the environment and the scannerpositioning, the initial rough scan can be omitted.

By way of another example of a multi-beam scanner with a spread of themeasurement beams inline with the scan direction, the returns of leadingbeams in scan direction may determine the density of the trailing beamsin scan direction. Thus, in a further embodiment also the scan speed maybe adjusted to allow for an even denser scan of the trailing beams.

By way of another example, e.g. in the field of autonomous driving, twodifferent multi-beam scan patterns are sent simultaneously, whereby onescan pattern uses diverging beams of a first wavelength formonitoring/collision avoidance and a second scan pattern of a secondwavelength is used for measuring/mapping the road.

According to one embodiment, the laser scanner comprises a deflectionelement configured for deflecting the multiple measuring beams in atemporally varying manner towards the environment.

According to another embodiment of the disclosure, the computing unit isconfigured to activate at least one of the at least two multi-beam scanpatterns based on at least one of a distance to an object in theenvironment to be scanned, a defined projected point density to beachieved by the scanning, e.g. projected onto an object to be scanned,and a defined object type of an object in the environment to be scanned.

In a further embodiment the computing unit is configured to activate atleast one of the at least two multi-beam scan patterns based on apre-programmed measuring process defining an activation and deactivationsequence of multi-beam scan patterns of the at least two multi-beam scanpatterns, in particular wherein the measuring process comprises at leastone of an initial evaluation of distance measuring data associated to atleast a first multi-beam scan pattern from the at least two multi-beamscan patterns and defining the activation and deactivation sequencebased on the initial evaluation, an initial scanning for identifying anobject within the environment to be scanned and defining the activationand deactivation sequence based on the identified object, determining aninitial positioning of the laser scanner, particularly with respect to apre-defined spatial reference point determined by a CAD system (CAD:“computer-aided design”), and adjusting a drive signal of the deflectionelement and/or a drive signal for adjusting an emission frequency of themeasuring beams, e.g. for adjusting a scan speed.

The laser scanner may further comprise a first zoom optics and/or afirst deformable lens element configured for setting differentmulti-beam scan patterns of the at least two multi-beam scan patterns,and/or the laser scanner may comprise a second zoom optics and/or asecond deformable lens element configured for aligning a beam of themultiple measuring beams with the receiver.

The zoom optics associated to alignment of the returning beams onto thereceiver may be reduced when large receiving arrays such as SPAD arraysare used. The zoom optics may particularly be configured to provideemitter-receiver alignment, for the purpose of setting different beamdistributions between multi-beam scan patterns, and/or for settingdifferent individual beam divergence angles of individual beams withinthe multi-beam scan patterns.

Another embodiment is characterized in that the transmitter comprisesmultiple laser diodes arranged on a carrier, particularly a curvedcarrier, the carrier has at least two different flexure states, andbased on different flexure states in each case the laser diodes generatedifferent multi-beam scan patterns of the at least two multi-beam scanpatterns. In particular, for each laser diode a congruent opticalreceiver or a congruent optical receiver area is provided.

For example, multiple laser diodes may be arranged on a piecewiseinclined surface, e.g. of an overall spherical shape, for creation of adivergent cone towards an inclined rotating deflection mirror deflectingthe multiple measuring beams in a temporally varying manner towards theenvironment. The arrangement can include a transmitter aligned to themechanical axis of rotation of the mirror (co-axial). Through thearrangement of the collimated laser diodes on the curved/piece wiseinclined surface, each diode has its own pitch and yaw angle relative tothe center axis of rotation of the mirror and each collimated laserdiode is paired with an individual photodetector. Depending on the interbeam angle, the beams may be converging at close range, meet at somedistance over a trajectory and then diverge. If the diodes are arrangedon a convex spherical surface the beams meet at the center point of thesphere spanning the surface, whereas when arranged on a concave surface,the beams diverge. By adjusting the inter beam angle by means ofadjusting the surface flexure, the coverage of the scanner can beoptimized to the measurement range, azimuth speed, and/or desired pointdensity. The returning light is deflected by the rotating mirror andgathered through a central focusing optics onto the plurality ofphotodetectors, wherein each photodetector has a small field of view toreduce the influence of background solar radiation and cross talk fromneighbouring beams. In addition, each detector channel may have its ownnarrow band optical wavelength filter.

In a further embodiment, also the detector elements, e.g. individualphotodetectors, are arranged on a curved surface, which eases theoptical requirements with regard to focusing and spot size/shape. Inparticular, by the arrangement of the detector elements on a curvedsurface, the use of simple spherical optics may be sufficient comparedto a-spherical optics (although flexible sensors are available). Theoptical receiving system can consist of refractive and diffractiveelements, wherein these elements can also be combined into a singlephysical part.

According to another embodiment, the transmitter is configured such thatthe multiple measuring beams comprise at least one of measuring beams ofat least two different wavelengths, measuring beams of at least twodifferent polarization states, and measuring beams having at least twodifferent pulse codings, in particular orthogonal pulse codings,particularly based on barker pulses.

Thus, to reduce optical cross talk, each laser diode may use a separatewavelength, or, to limit the amount of different components, two or morewavelengths may be used in such a manner as the wavelength alternatessuch that at least adjacent laser beams have a different wavelength.

Furthermore, as the reflection characteristics of many surfaces varywith wavelength, the use of multiple wavelengths has added benefit inthat it gives the opportunity to spectrally classify the reflectionproperties of surfaces.

For example, using “white” light transmitters, it is possible to havemore complete information of the same surface region, e.g. by usingabsorption stacks to distinguish between different wavelengths at thesame exposed surface area of the detector. However, as the sensitivityof such photo-sensitive stacks is low, e.g. as compared to thesensitivity from avalanche photodiodes, such a system has a reducedrange. The range of the system may be extended in that the distanceresults of the detector stack are averaged.

The use of multiple polarization states/multiple polarizers is a furthermethod to differentiate between multiple beams emitted at the same time.However, the generally uncontrolled incident angles of a scannerscanning an unknown environment often introduces ambiguity becausechanges of the polarization state of the incident beam can happendepending on the angle of incidence and the material of the scannedobject.

An additional measure to reduce crosstalk influence is by sending codedpulses. For example, often the entire waveform of the analog signal ofthe radiation detected by a detector is sampled by means of theso-called wave form digitizing method (WFD). In WFD a signal istransmitted, e.g. in the form of a single pulse or by a pulse codingsuch as a defined sequence of pulses or a defined modulation of pulses,wherein the returning signal is detected by means of sampling the signalprovided by the receiver. After identification of the single pulse orthe coding of the associated transmission signal (ASK, FSK, PSK, alsoknown as distance or interval modulation, etc.) of a received signal thesignal propagation time (“pulse propagation time”, ToF) is determined,e.g. by means of the Fourier transformation or based on a defined pathpoint of the sampled, digitized and reconstructed signal path, such asthe turning points, curve maxima, or integrally by means of an optimumfilter known from the time interpolation.

Examples of time-resolving signatures are center of gravity, sine-cosinetransformation, or amplitude-defined FIR filters (“finite impulseresponse filter”) with a weight coefficient derived from the pulseshape. To reduce any distance drift a corresponding time-resolvedsignature may also be compared with an internal start signal. To reduceirreversible sampling errors, additional digital signal transformationsknown to one skilled in the art may be used.

One of the simplest modulation modes is the marking of the individualpulses or the pulse sequences by distance coding, e.g. as described byEP 1 832 897 B1, which may be used for the purpose ofre-identifiability. This recognition is desired when an ambiguity ariseswhich may be caused by different scenarios occurring during atime-of-flight of pulses, e.g. if there is more than one pulse or apulse group between the measuring device and the target object. Anotheravailable method for ambiguity resolution related to multiple pulses inair may include the time interval coding of short burst sequences, e.g.the distance between emitted pulse pairs as described by EP 3 118 651A1.

Depending on the number of transmitters, the allowable eye-safetylimits, and the desired range, each individual transmitter can have aseparate unique code. To reduce the number of unique codes, the codedpulses are sent in such a way that adjacent transmitters send orthogonalpulses. For example, when using barker pulses, the extended pulse lengthdoes not affect the sharpness of the correlation peak when compared withsending of a single pulse. Barker pulses may also be beneficial in caseswhere the eye safety would allow for more laser power, whereas the peakpower of the laser diode is at its limit. In such a case sendingmultiple pulses, for instance barker pulses, can result in a betterchannel separation and an increased signal-to-noise ratio (S/N).

Alternatively or in addition, by using holographic structures the numberof transmitters may be reduced, e.g. by using holographic structures, adiffractive optical beamsplitter, and a single transmitter in the beamforming process. Therefore, instead of using a diode for each beam andwavelength, a hologram may be used.

In a further embodiment, the transmitter comprises one or multipleradiation sources, particularly the multiple radiation sourcesgenerating radiations of different wavelengths. The transmitter furthercomprises a holographic structure and is configured for generating afirst and a second group of beams based on the holographic structure,particularly wherein the first group of beams is generated based on afirst radiation source and the second group of beams is generated basedon a second radiation source. According to this embodiment, thetransmitter and the computing unit are configured that one multi-beamscan pattern of the at least two multi-beam scan patterns is based onthe first group of beams and another multi-beam scan pattern of the atleast two multi-beam scan patterns is based on the second group ofbeams.

In particular, according to another embodiment, the receiver comprisesan objective lens, wherein the transmitter comprises the first and thesecond radiation source, particularly the first radiation sourcegenerating radiation of a different wavelength than the second radiationsource. The transmitter is configured to generate the first group ofbeams based on the first radiation source and to generate the secondgroup of beams based on the second radiation source, wherein theholographic structure is configured that the beams of the first and thesecond group of beams emanate from a circumferential area surroundingthe objective lens.

The same hologram may be used for different wavelengths, wherein thedistribution of the resulting beams will then be different. For example,using a beam combiner to combine the laser sources prior to illuminationof the hologram (like a fibre for instance) it would be possible to usethe same hologram at the same location. In particular, multipleholograms can be integrated into a single physical element.

By way of another example, using radiation sources of differentwavelength, a single hologram is illuminated for each wavelength by aseparate laser. Because of the multiplication factor of beams projectedby the hologram, groups of beams of the same wavelength are generated.The beam groups are mixed in the monitored zone so that there is nooverlap of projected beams of the same group/wavelength in the monitoredzone.

Furthermore, it is also possible to differentiate between the channelsby other means, e.g. by code sequences, wherein the first group of beamsis linked to a first diode emitting a first code, and a second group islinked to a second diode emitting a second code. In the monitored zone,physically, the beams of a group are not located together but mixed withthe beams of the other groups. The group of beams may emanate from asimilar local region/from a single hologram. The orientation of thebeams is then chosen so as to achieve the correct mixing of the beamalignments in the monitored zone. Both methods, e.g. multiplewavelengths and code sequences for differentiation of adjacent beams,can be combined.

By way of example, multi-color back reflections, of which the beams areemitted by an apparently similar source or source direction, originatingfrom the same or overlapping target area can be split at the receiverusing for instance prisms or holographic dispersers. Using the hologram,cost and size of the transmitters may be reduced while maintaining thechannel separation. In a distributed system concept in which the emittedbeams surround the receiving optics, light guides/light fibers are usedto deliver the beams emanating from a diode to the target hologram, e.g.arranged around a deflecting mirror. The light guides/light fibers canbe used to combine multiple laser sources.

In a further embodiment, the holograms aligned to the transmitters areinterchangeable, wherein through the variation of the holograms, theprojection scan pattern is adjusted for optimization of the projectionscan pattern in the monitored zone. For example, the optimization may beone of better point distribution with respect to the anticipated targetshape (angle coverage) and distance, power distribution and thereforethe range of the measurement. Actuators may be used for changing of theholograms, wherein the holograms may be arranged on a single surfacethrough which a single actuator may be used for selection of a suitablehologram group, e.g., wherein a hologram group is a collection ofholograms aligned to one or multiple radiation sources.

By way of another example, using a holographic grating, a (divergent)point source can be used to generate a collimated beam. By usingmultiple collimated beams with different inter beam orientation andspacing as the object source during hologram creation, multiplecollimated object beams are reconstructed from a single point source,wherein the lateral position and inter orientation of the beams isdetermined during the creation of the hologram. When selectively usingmultiple holograms, each created with different lateral spacing and/orvarying inter orientation of the beams and/or varying divergence of eachbeam, multiple emission patterns can be projected.

Re-creating (collimated) beams through the hologram makes it possible tocollimate the beams without additional optical elements and holderstherefore, wherein placing a light source at a different position(angle) compared to the position at the time of creation of the hologramcreates a reconstructed beam at a different wavelength.

According to another embodiment, the receiver comprises anopto-electronical sensor based on an arrangement of a multitude ofmicrocells, particularly wherein the sensor is configured as an array ofsingle photon avalanche photodiodes, the sensor is configured such thatthe microcells can be read out individually or in groups of microcells,such that sub-areas of the receiver are settable which can be read outseparately, and the receiver and the computing unit are configured thatdifferent sub-areas of the receiver are set by the computing unit,namely in such a way that returning parts of different measuring beamsof the multiple measuring beams in each case are read out by differentsub-areas of the receiver.

For example, arrays of single photon avalanche photodiodes, in thefollowing called SPAD arrays, are usually arranged as a matrix structureon a chip. The devices or chips with a photosensitivity in the visibleand near infrared spectral range are also referred to as SiPM (SiliconPhotomultiplier). The SiPM gradually replace the photomultiplier tubesused hitherto, in particular in the visible and near ultravioletspectral range. SiPM have a high spectral sensitivity in the visiblewavelength range. For example, silicon-based SPAD arrays produced inCMOS technology are available, which are sensitive up to thenear-infrared range beyond a wavelength of 900 nm.

Commercial SPAD arrays are also available at wavelengths between 800 nmand 1800 nm. These sensors mainly consist of the InGaAs semiconductormaterial. Depending on the design, these sensors also have an externalor internal matrix structure over the photo-sensitive surface. Distancemeasuring systems with SPAD arrays in this spectral range have theadvantage that the solar backlight (daylight) is significantly lowerthan the visible wavelength range and that this disturbing luminous fluxis less detrimental to the SPAD arrays.

The special feature of these SPAD array sensors is their highphotosensitivity, whereby the SPAD arrays are mainly designed to detectsingle photons without problems. Therefore, they are also referred to as“multipixel photon counters” (MPPC). The SPAD arrays consist ofhundreds, thousands, and tens of thousands of microcells and are capableof simultaneously receiving pulses with thousands or hundreds ofthousands of photons. In addition, due to the parallel connection of themany microcells into cell groups (domains), sufficient cells are stillavailable for detecting the signal photons even in the case of solarbackground light.

A further special feature of SPAD arrays is that individual microcellsor individual subsets of microcells can be separately controlled and/orseparately read out. The microcells can thus be activated locallysequentially, e.g. for a line- or column-wise readout of the receiver(for example as a “rolling shutter” or “rolling frame”).

In particular, subsets of microcells may be defined by a group ofadjacent microcells, or the subregions may be defined by spaced-apartregions of the receiver, e.g., such that the individual subregions aredefined by separate unconnected spatial groups of microcells.

Therefore, by using a SPAD array with individually addressablemicrocells, the active region of the SPAD array can be configured tomatch the selected alignment of an associated beam of the multiplemeasuring beams of the inventive laser scanner. Thus, the individualmicrocells of the SPAD array are grouped/selected so as to match theselected alignment/shape of the individual beams.

In addition, a time sequence of signal capturing may be generated inthat individual microcells or microcell groups (domains) of the SPADarray are alternately led to the output, e.g. by alternating even andodd lines of the SPAD array. Such a time-alternating activation ofmicrocells or microcell groups shortens the recovery time of the SPADarray, whereby a faster laser modulation or pulse shooting rate can beachieved.

Instead of activating the microcells or microcell groups (domains) ofthe SPAD array, they can remain activated in a stationary state, forcapturing and evaluating the output of the microcells or domainssynchronously to the scanning movement. In this case, the microcells ormicrocell groups (domains) are directly connected to the signal output,which are aligned in time-synchronous manner with respect to the surfaceof the object, by means of an electronic circuit, for example integratedon the SPAD array.

The respectively active FoV of the receiving unit is designed so smallin the angular range that the backscattered receiving pulses can becompletely viewed and received and, as little as possible, disturbingambient light is received.

In the literature a distinction is made between SPAD array operations inlinear mode, Geiger mode and SPL mode (SPL, “Single Photon Lidar”).

In the linear mode below the breakdown voltage, a gain occurs whichdepends on a blocking voltage and temperature, wherein SPAD arrays inlinear mode can be used for the construction of a high-sensitivityphotoelectric receiver with an output voltage proportional to theradiation input.

In Geiger mode and SPL mode, e.g., in operation above the breakdownvoltage a SPAD or SPAD arrays can be used for single photon counting. Ina SPAD in Geiger mode, each individual pixel generates an output signal,whereby the electron avalanche is triggered by exactly one photon. If aphoton packet consists of several photons, then no larger signal ismeasured. Therefore, no amplitude information is available.

In the Geiger mode, an incident photon packet produces a (binary) eventsignal, which is not proportional to the amount of photons in the photonpacket.

SPL mode is a SPAD array operated in Geiger mode where many microcellsare connected in parallel to an output signal. In the case of incomingphoton packets with a few photons, the individual avalanches add upvirtually linearly and the amplitude of the output signal is thereforeproportional to the number of detected photons.

The recovery time of the microcells after a photonic trigger is not zerobut, for example, between 5-50 nanoseconds, which reduces the apparentsensitivity of the SPAD array for subsequent photons. However, this hasthe advantage, for example, that the sensor can detect a signal strengthrange with high dynamics. For SPAD arrays with a large number ofmicrocells (>1000) this non-linearity is monotonic and, on the one hand,leads to an amplitude compression between the input signal and theoutput signal, and, on the other hand, with increasing input signal, toa weakened increasing output signal. Interestingly, the output signal ofSPAD arrays with a high number of microcells (>1000) does not completelysaturate so that an amplitude change can be measured even with areception pulse with a high photon number well over one million.

The laser signals of a distance measuring device are generally subjectedto pulse coding. Experiments have shown that such signals can be wellreceived with SPAD arrays at voltages in the overbreak mode. Also Pulsepackets (bursts) can be received unambiguously and almost noise-free.For example this is also the case, when the recovery time of themicrocells is quite long, e.g. ten nanoseconds. Due to thequasi-analogous construction of SPAD arrays, a photo current which ispresent due to ambient light is also received. The laser signal is thensuperimposed on the electrical photo current of the ambient light. Forexample, the current pulse generated by the laser pulse may be high-passfiltered at the output of the SPAD array, so that the slow falling edgesignal is shortened. The output pulse thereby becomes a short signalpulse, e.g. with a pulse duration less than a nanosecond. Such shortpulses with steep edges are suitable for precise time and distancemeasurements. However, the use of a high-pass filter (differentiator)does not affect the recovery time of the SPAD array.

Furthermore, initial implementation attempts have already beenundertaken to integrate more electronic functionality into the SPADarrays. By way of example, time-measuring circuits (“TOF-circuitries”,TDC: “time to digital converter”) assigned to each microcell are alreadyused. These measure the runtime (TOF, “time-of-flight”). SPAD arrayimplementations exist, for example, where precise photon counting isintegrated in the vicinity of the microcells, which do not require adownstream analog-to-digital converter (ADC). In addition, atime-measuring circuit (TDC) may for example be integrated in eachmicrocell. Further, a digital interface may be used as output of theSPAD array. For example, such devices are fully digital and do not needmixed signal processing during CMOS production.

According to another embodiment, the receiver comprises multipleopto-electronical sensors, particularly multiple arrays of single photonavalanche photodiodes, wherein the multiple sensors are arranged in aone-dimensional, a two-dimensional, or a three-dimensional manner, inparticular wherein each sensor has its own control electronics,particularly also its own evaluation electronics.

For example, the individual sensors may be integrated into a singlehousing, forming an array of photo-active regions of which theorientation of the active region is linked to the transmitter throughthe optics. Such a receiver array may consist of a coherenttwo-dimensional array of detectors with regular equal and/or unequalspacing between the active elements constituting the array (so-calledmega-array), wherein the alignment of the receiving array and theindividual beams of the transmitter is made during the manufacturingprocess and can be dynamically changed depending on a chosen zoom, interbeam divergence, and the divergence of each individual beam.

In a further embodiment, the laser scanner comprises a customizablecomponent, particularly an integrated circuit, wherein the customizablecomponent comprises an optically active element formed by at least oneof a customizable emitter array, particularly a VCSEL or a VECSEL array,configured to form a customizable emitting component for generating atleast one beam of the multiple measuring beams, and a customizablereceiving array, particularly an array of single photon avalanchephotodiodes, configured to form a customizable receiving component fordetecting returning parts of the multiple measuring beams, particularlywhereby the receiving array is integrated onto the same integratedcircuit as the emitter array.

For example, the laser scanner comprises a plurality of suchcustomizable components, wherein each customizable component isconfigurable by software such that customizable components are groupedto at least one common receiving component and/or to at least one commonemitting component.

Therefore, by way of example, the receiving array, e.g. a SPAD array, iscombined with an emitter array on the same chip/wafer. The emitter arraymay be a VCSEL (vertical-cavity surface-emitting laser) or VECSEL(vertical-external-cavity surface-emitting laser) array. For instance,the collimation of the VCSEL array into a singular beam can beaccomplished by a microlens array on wafer scale as a light gatheringand pre-collimation lens array combined with a macroscopic lens.

Using the VCSEL/VECSEL structure as a receiving element of atime-of-flight sensor, the vertical cavity structure of the VCSEL/VECSELmay be used as a natural narrow-band optical filter element into which aphotosensitive element has been integrated, e.g. an APD detector or SPADdetector. This way, each active component of chip/wafer can beselectively used for detection purpose, for example only, and not as anemitter, wherein the selection of which is controlled by software.

Thus, part of the integrated chip is selectively configured as lightemitter whereas the other part is selectively configured as a lightreceiver. Individual emitting VCSELs can be grouped into a singularlight emitting beam. Likewise, the non-emitting VCSELs with added lightsensitive elements can be grouped into a singular receiver. Using bothrefractive and diffractive elements, it is also possible to arrange formultiple beams in different angular directions from the same chip. Usingthe same refractive and diffractive elements, the receiver can beconfigured to view in the same directions of the emitters. Also in anoff-axis design it is possible to activate VCSELs at a spatiallydifferent location on the chip, which results in a different spatialorientation of the resulting laser beam. Likewise, the receiving part ofthe VCSEL array can be shifted by software to the correct lateralposition on the same chip.

In a further embodiment, the integrated chip is configured thatdifferent wavelengths are integrated in different regions of the chip.This can for instance be accomplished with VECSELS by placement of theexternal cavity at a different distance.

Another embodiment relates to a combination of the integrated chip witha hologram.

In a further embodiment, the integrated chip—with or without hologram—iscombined with a zoom lens with which the divergence of the emitted beamscan be altered.

In an even further embodiment, the VCSEL cells are configured as abottom emitter whereas the integrated receiver is a top emitter. Thisarrangement is no longer capable of configuring the whole active area asreceiver and/or emitter, whereas the selective activation of theindividual optically active elements of each array remains. For example,an advantage of this packaging arrangement is that the emitter elementand the receiver element are pointing in opposite directions and straylight reflected off the optics for beam collimation no longer interferewith the receiving elements.

The alignment of many transmitting elements to many detectors duringassembly is an elaborate task. This alignment may be accomplishedthrough mechanical means, wherein the alignment process duringmanufacturing and subsequent testing of the stability during thedevelopment phase are significant cost drivers.

Following the mechanical alignment, the components are to be held inplace mechanically. Usually this process is executed by a human operatoror through an automated process. Using an electrically conductive glue,the fixation process can be actuated in a fast and reliable manner bysending a fixation command to an intelligence involved in the automationprocess which then sends an adequate current through the area involved.This process can be executed by the intelligence integrated onto thesame board used for evaluation of the measurement signals and generationof the emitted pulses. This in-place fixation process after alignmentresults in simultaneous cost savings and quality improvement during themanufacturing of the device.

For example, by using a zoom optics the grid of the transmitters can bealigned to the grid of the detectors. The placement of the optical partsonto the circuit boards may be controlled with adequate placementtolerances, wherein the zoom optics is used to correct for the normaltolerances during production and assembly.

In particular, a classical zoom arrangement through manually moveablelenses may be sufficient and encompass only the receiving optical path.After alignment the mechanical position of the zoom lenses are fixed.Furthermore, the zoom of the receiving lens may be set usingelectronical means, for instance by setting the curvatures of adeformable lens element like a liquid lens. For example, this has theadvantage in that the time taken and the skill used during assembly aremuch less compared to a manual process. In addition it is possible tocorrect for possible misalignment of the transmitters and receiversduring the lifetime of the device or due to temperature variations.

By way of another example, a zoom optics is provided onto thetransmitter and electronically actuated and controlled. By means of thezoom optics on the transmitter, the divergence of the beams is alteredfrom a collimated state to a divergent state. In the diverging state,the beams encompass a large field of view and are, for example, suitablefor collision detection and avoidance purposes. In the case when havinga rotating mirror for beam deflection, due to the rotation of the mirrorand the known 90° rotation of the projected beams, it can be sufficientto have cylindrical zoom optics by which the generated collimated beamsare only divergent in a particular direction. Furthermore, theorientation of the transmitted beams to the rotational axis can bevaried and a steering of the emitted beams is accomplished through theuse of said zoom optics, wherein actuation of the emitting and receivingzoom optics may take place simultaneously/congruently. For instance, byusing a liquid lens on the emitter optics, the variation of theorientation of the emitted beams and their divergence can be combined ina singular optical element.

In another embodiment, the laser scanner is configured to providesimultaneous scanning with a first and a second multi-beam scan patternof the at least two multi-beam scan patterns, in particular wherein therepetition rate for deriving distance measuring data based on the firstscan pattern is different from the repetition rate for deriving distancemeasuring data based on the second scan pattern.

For example, the first scan pattern may provide a set of diverging beamsof a first wavelength, and the second scan pattern may provide a set ofbeams of a second wavelength, said second wavelength being differentfrom the first wavelength.

BRIEF DESCRIPTION OF DRAWINGS

The laser scanner according to the disclosure is described or explainedin more detail below, purely by way of example, with reference toworking examples shown schematically in the drawing. Specifically,

FIG. 1 a-c : schematically depicts different applications of theinventive multi-beam laser scanner;

FIG. 2 a,b : schematically depict an inventive multi-beam laser scannercomprising multiple laser diodes arranged on a carrier having at leasttwo different flexure states;

FIG. 3 : schematically depicts an inventive multi-beam laser scannercomprising a beamsplitting hologram and a SPAD-based receiver;

FIG. 4 : schematically depicts an integrated chip being configurable bysoftware and having an emitter array and a receiving array;

FIG. 5 : schematically depicts an active component with selectiveactivation of emitters or groups of emitters and receivers or groups ofreceivers on a VCSEL array and chip.

DESCRIPTION OF EXAMPLE EMBODIMENTS

FIG. 1 a shows an example laser scanner 1 in the field of buildingsurveying, here with two rotary axes 2A,2B, e.g., a so-called slow(vertical) axis of rotation 2A—also referred to as the azimuthalrotation axis—and a so-called fast (horizontal) axis of rotation 2B. Thelaser scanner 1 comprises a base 3 and a support 4, wherein the support4 is mounted on the base 3 in such a way that is rotatable around theslow axis 2A. The laser scanner further comprises a fast-rotating beamdeflection element 5 mounted in the support 4 of the laser scanner 1 insuch a way that it is rotatable around the fast axis 2B.

By way of example, e.g. for scanning linear or linearly drivablestructures and environments such as track systems, roads, tunnel systemsor flight fields, the base and thus the azimutal rotation axis 2A may beomitted. Instead, the laser scanner may be mounted on a transportingmeans, for example a ground- or air-supported carrier vehicle. Such alaser scanner with only one beam axis of rotation may be referred to asa profiler.

In particular, profilers but also two-axis laser scanners for a coherentmeasurement of a large area often have additional position andorientation means, e.g. directly integrated in the laser scanner, toautomatically reference local scanning data with a global 3D coordinatesystem.

Furthermore, laser scanners may comprise a camera, e.g. for detectingRGB data, whereby the camera images of the environment can be linked tothe scanning data generated by the distance measuring beam andassociated angular encoder data for the direction of the distancemeasuring beam. For example, the camera can be individually movable,e.g. to detect different field of views and/or to orient the camera dataand the scanning data with respect to a common reference surface or acommon coordinate system.

According to the disclosure, the laser scanner 1 is configured togenerate a plurality of beams 6 for scanning at the same time.Therefore, a higher point rate or a higher point density may be achievedwith a slower rotation speed of the rotating deflection element 5.Furthermore, the laser scanner is configured to provide scanning with atleast two different multi-beam scan patterns 7A,7B, based on themultiple measuring beams 6, wherein each multi-beam scan pattern 7A,7Bis individually activatable.

For example, as shown by the figure, the multi-beam scan patterns 7A,7Bmay differ from each other in that, compared to each other, they providea different number of beams and a different spreading direction of theindividual beams, e.g. to set a different projected beam density and adifferent projected beam distribution on the target object. In the givenexample, the laser scanner may have been provided with rough pre-scaninformation, e.g. wherein the scanner comprises a pre-programmedscanning process involving a rough pre-scan with object identificationand a subsequent measuring scan, and thus increase the point density forscanning objects like doors or windows, whereas for scanning blank wallsthe point density can be decreased to reduce data volume and computingpower.

In another example the spreading of the beams is used to determinedistance variances based on the leading beams for adjusting a scandensity by the trailing beams. In yet another example the scan densityof the (trailing) second beam set is set by the distance returns of thefirst (leading) beam set.

FIG. 1 b shows another example airborne measurement based on aninventive LiDAR scanner 1′ on board an airborne carrier 8, e.g. anairplane, for scanning with multiple LiDAR beams 6, e.g. here in a“staring” 2D configuration with a fixed viewing direction of the laserscanner 1′. This kind of configuration may be useful when usinglight-sensitive detectors such as in SPL applications. Multi-element(multi-pixel) detector devices are able to detect an incident flux oflight (down to a single photon) providing information for each pixel onthe number of photons and their arrival times. For example, the multipleLiDAR beams 6 are produced from a single transmitted laser pulse whichthen illuminates a ground surface area 9,9′ with a size that isdependent on the flying altitude and the laser aperture. These kinds ofaerial LiDAR systems have the advantage that, thanks to the highdetector sensitivity, low energy laser beams can be used and scanningcan be performed from high altitudes. Since each surface point isscanned from many different viewing angles shadow effects are greatlyminimized.

Alternatively, a variable deflection element may be used to generate anadditional scanning movement of the multiple LiDAR beams, e.g. a simple“zig-zag” scan by using a sweeping deflection mirror or more elaboratedscan movements such as a circular scanning (“palmer scan”). For example,the latter may have the advantage that with one flyover, each measuredsurface point can be detected from two different viewing angles. Thisminimizes shadow effects, wherein a large area can be scanned at thesame time with low energy laser pulses of even less energy than with thestaring scanner configuration.

The surface is mapped, whereby different scanning patterns 7A,7B may beactivated depending on flight altitude, and desired point density.

For example, the laser scanner 1′ can thereby access further data fordetermining a relative or definite position of the laser scanner, e.g.data of inertial sensors provided by the carrier 8, altitude measurementdata or data from a global positioning system. Furthermore, an availabledigital 3D model of the overflown terrain might be stored on a centralcontrol device of the airplane 8 or on a control and processing unit ofthe aerial laser scanner 1′. The laser scanner 1′ may also have its ownpositioning measurement means or inertial measurement sensors fordetecting self-movement of the laser scanner 1′.

The additional data may be partially processed by a computing unit ofthe carrier 8, or the laser scanner 1′ may be configured to directlyprocess the provided data, e.g. wherein a computing unit of the laserscanner continuously derives the position and orientation of the scannerand generates a movement profile of the laser scanner 1′ and determinesits position with respect to the surface to be measured.

FIG. 1 c shows a further application of the laser scanner 1″ accordingto the disclosure in the area of autonomously traveling vehicles,wherein the roads to be driven may be recorded in advance by a dedicatedLiDAR module 1″ mounted on a vehicle 8′ and the measurements areprovided to a model generator. In such a laser scanner 1″ the horizontalfield of view 10 may be larger than the vertical field of view 11,wherein the acquisition rate for the scanning of the complete field ofview may for example be approximately 25 Hz.

Such systems may include a robust and long-lasting design of the laserscanner, whereby also a compact design may be desired, and, wherepossible, moving parts are omitted. Thus, often MOEMS components(“micro-opto-electro-mechanical system”) or adjustable or deformablerefractive optical elements, e.g. liquid lenses, are used as deflectingelements here. In accordance with these specifications, by way ofexample, the inventive use of a SPAD-array sensor has the advantage thatthe opto-mechanic design of the receiving channel may be furthersimplified.

According to the disclosure, the laser scanner 1″ may for example beconfigured to provide simultaneous scanning with a first 7C and a second7D multi-beam scan pattern, e.g. wherein the repetition rate forderiving distance measuring data based on the first scan pattern 7C isdifferent from the repetition rate for deriving distance measuring databased on the second scan pattern 7D.

For example, the first scan pattern 7C may provide a set of divergingbeams of a first wavelength, which beams are particularly used forcollision avoidance purposes, and the second scan pattern 7D may providea set of converging beams of a second wavelength, said second wavelengthbeing different from the first wavelength, wherein the beams of thesecond scan pattern 7D are particularly used for mapping the road.

FIG. 2 a,b schematically show a multi-beam laser scanner comprisingmultiple laser diodes arranged on a carrier having at least twodifferent flexure states, FIGS. 2 a and 2 b depicting different flexurestates of the carrier.

For example, multiple laser diodes 12 may be arranged on a piecewiseinclined surface 13 for creation of a divergent cone towards an inclinedrotating deflection mirror 5 deflecting the multiple measuring beams 6in a temporally varying manner towards the environment. Each diode 12has its own pitch and yaw angle relative to the center axis 14 ofrotation of the mirror 5, wherein each laser diode 12 is paired with anassociated detector or an associated receiving area of a detector 15having multiple subareas for readout.

By adjusting the inter beam angle by changing the surface flexure, thecoverage of the scanner is optimized to the measurement range, azimuthspeed, and/or desired point density. The returning light 17 is deflectedby the rotating mirror 5 and gathered by an objective 18 and a centralfocusing optics 19 onto the plurality of receiving areas of the detector15, in particular wherein each receiving area has a small field of viewto reduce the influence of background solar radiation and cross talkfrom neighbouring beams.

In addition, the diodes 12 may be configured to provide measuring beamsof different wavelength and/or additional optics 20 may be used, e.g.filters with regard to wavelength and/or polarization to reduce opticalcross talk effects or variable zoom optics for beam alignment purposes.Similarly, each detector channel may have its own narrow band opticalwavelength filter (not shown).

Furthermore, a computing unit 21 is indicated, the computing unit 21being configured for controlling the laser scanner to provide a scanningof the environment by the multiple measuring beams 6, for derivingdistance measuring data based on the multiple measuring beams 6, and forderiving angle data for respective emitting directions of individualmeasuring beams of the multiple measuring beams 6.

By way of example, the computing unit 21 is configured to activatedifferent multi-beam scan patterns based on a distance to an object inthe environment to be scanned, a defined point density to be achieved bythe scanning, and/or a defined object type of an object in theenvironment to be scanned.

For example, the computing unit 21 may further be configured to providescanning according to a pre-programmed measuring process defining anactivation and deactivation sequence of multi-beam scan patterns, e.g.wherein the measuring process comprises an initial scanning foridentifying objects within the environment to be scanned as well as aninitial determining of distances to the identified objects. Such aninitial scanning process may involve the step of determining thedistances returned by a first set of (leading) beams to determine thescan density of a second (trailing) set of beams.

In addition, using the a-priori knowledge of the target distance in acertain direction as described earlier, instead of using the emitters assingle radiation sources each with a different direction, two or moreradiation sources may be grouped together and pointed in the samedirection to the same point on the target. By using the grouped lasersources in a cooperative manner, the target can be illuminated with ahigher intensity while still achieving eye safety. Furthermore by alsogrouping the congruent receivers an even better signal to noise ratiocan be achieved resulting simultaneously in an even further range andimproved (smaller) variation of the measured distance.

FIG. 3 schematically shows an inventive multi-beam laser scannercomprising a beamsplitting holographic structure 22 and a SPAD-basedreceiver 15′ being configured such that multiple sub-areas of thereceiver 15′ are definable which can be read out separately. In thegiven example, the transmitter is based on a single radiation source 23.Alternatively, the transmitter may also be based on multiple radiationsources, e.g. of different wavelength.

By using holographic structures the number of radiation sources may bereduced. Because of the multiplication factor of beams projected by thehologram 22, groups of beams 6 of the same wavelength are generated.Additional differentiation between the channels may, for example, begenerated by code sequences, wherein the first group of beams is linkedto a first diode emitting a first code, and a second group is linked toa second diode and emitting a second code.

By way of example, multi-color back reflections, of which the beams areemitted by an apparently similar source or source direction, originatingfrom the same or overlapping target area can be split at the receiverusing for instance prisms or holographic dispersers. Using the hologram,cost and size of the transmitters may be reduced while maintaining thechannel separation.

The holograms aligned to associated radiation sources 23 may beinterchangeable, e.g. wherein holograms are arranged on a single surfacewhereby a single actuator may be used for selection of a suitablehologram group, wherein through the variation of the hologram 22, aprojection scan pattern is adjusted for optimization of the projectionscan pattern in the monitored zone.

The figure further indicates the plane 24 of the beamsplitting hologram22, the receiving plane 25 comprising the detector 15′, and a receivingoptics 18 for gathering and aligning returning beams 17 towardsassociated receiving areas 26 of the SPAD detector 15′.

For example, in such a side-by-side holographic projector and receivermulti-axial morphology the distance between the receiving plane 25 andthe hologram plane 24 may be reduced to zero, wherein the receivingelements are mounted to the back of the hologram 22. However, this mayreduce reproduction quality.

FIG. 4 schematically shows a chip 27 having an emitter array 28, e.g. aVCSEL or VECSEL array, and a receiving array 29, e.g. a SPAD array. Thechip 27 is configurable by software, e.g. controlled by a computing unitof the inventive laser scanner, such that it may be used either as areceiving 30 and/or as an emitting 31 component.

For instance, the collimation of a VCSEL array 28 into a singular beamcan be accomplished by a microlens array (not shown) on wafer scale as alight gathering and pre-collimation lens array combined with amacroscopic lens (not shown).

Thus, as shown by FIG. 5 , part of the integrated chip 27 is selectivelyconfigured as light emitting component 31 whereas the other part isselectively configured as a light receiving component 30. By way ofexample, individual emitting VCSELs can be grouped together into asingular light emitting beam. Likewise, the non-emitting VCSELs, usingthe light sensitive elements integrated into each VCSEL element, can begrouped into a singular receiver. Using both refractive and diffractiveelements, it is also possible to arrange for multiple beams in differentangular directions from the same chip. For example, by using the samerefractive and diffractive elements, the receiver may be configured toview in the same directions of the emitters. Alternatively, an off-axisdesign relative to a macroscopic optical element/acroscopic opticalelement array may be chosen resulting in a selectively different spatialorientation of the resulting laser beam with respect to the central axisof the macroscopic element. By arranging different lateral positions ofthe emitter components relative to the central axis of the macroscopicoptical element by the software, different spatial orientations of theemitted beams result.

FIG. 5 schematically shows individual optically active elements 32 of achip 27 (FIG. 4 ) on a wafer 33. Each optically active element 32 can beconfigured by software, e.g. controlled by a computing unit of theinventive laser scanner, to act as a receiver and/or emitter. Multiplecongruent active elements can thereby be grouped together to form areceiving component 30 or an emitting component 31.

By timely varying the selected elements constituting the receivingcomponents 30 and the emitting components 31 a scanning motion can beaccomplished.

Although the disclosure is illustrated above, partly with reference tosome preferred embodiments, it should be understood that numerousmodifications and combinations of different features of the embodimentscan be made. These and other modifications lie within the scope of theappended claims.

What is claimed is:
 1. A laser scanner for optical surveying of anenvironment, comprising: a multibeam transmitter configured to provideat least two different multi-beam scan patterns being individuallyactivatable by a computing unit, wherein each of the two multi-beam scanpatterns comprises simultaneously generated multiple measuring beamsdefining multiple substantially instantaneous scanning axes; adeflection element configured to deflect the multiple measuring beams ofthe two scan patterns in a scan direction, a receiver configured todetect returning parts of the multiple measuring beams of each of thetwo scan patterns; and the computing unit configured: for controllingthe laser scanner to provide scanning of the environment by the multiplemeasuring beams, for deriving distance measuring data based on themultiple measuring beams, and for deriving angle data for respectiveemitting directions of individual measuring beams of the multiplemeasuring beams, wherein: the at least two different multi-beam scanpatterns differ from each other in that, compared to each other, the atleast two different multi-beam scan patterns provide a differentprojected beam density, and the transmitter is configured such thatwithin each of the two scan patterns, multiple simultaneously generatedmeasuring beams comprise simultaneously generated adjacent measuringbeams, wherein simultaneously generated adjacent measuring beams differby at least one of: wavelengths; polarization states; and pulse codings.2. The laser scanner according to claim 1, wherein the multi-beam scanpatterns differ from each other in that, compared to each other, themulti-beam scan patterns provide at least one of: a different number ofbeams; a different projected beam distribution; a different beamspacing; a different emission timing; different individual beam shapes;and a different spreading direction of the beams.
 3. The laser scanneraccording to claim 2, wherein: the multi-beam scan patterns differ fromeach other in that, compared to each other, the multi-beam scan patternsprovide a different spreading direction of the beams, one multi-beamscan pattern is provided as a set of beams which converge to each othersuch that the beams have a common point of intersection in a propagationdirection of the beams, and another multi-beam scan pattern is providedas a set of beams which diverge from each other.
 4. The laser scanneraccording to claim 1, wherein the computing unit is configured toactivate at least one of the at least two multi-beam scan patterns basedon at least one of: a distance to an object in the environment to bescanned; a defined projected point density to be achieved by thescanning; and a defined object type of an object in the environment tobe scanned.
 5. The laser scanner according to claim 1, wherein: thecomputing unit is configured to activate at least one of the at leasttwo multi-beam scan patterns based on a pre-programmed measuring processdefining an activation and deactivation sequence of multi-beam scanpatterns of the at least two multi-beam scan patterns, and the measuringprocess comprises at least one of: an initial evaluation of distancemeasuring data associated with at least a first multi-beam scan patternfrom the at least two multi-beam scan patterns, and defining theactivation and deactivation sequence based on the initial evaluation; aninitial scanning for identifying an object within the environment to bescanned, and defining the activation and deactivation sequence based onthe identified object; determining an initial positioning of the laserscanner; and adjusting a drive signal of the deflection element and/or adrive signal for adjusting an emission frequency of the measuring beams.6. The laser scanner according to claim 1, wherein: the laser scannercomprises a first zoom optics and/or a first deformable lens elementconfigured for setting different multi-beam scan patterns of the atleast two multi-beam scan patterns; and/or the laser scanner comprises asecond zoom optics and/or a second deformable lens element configuredfor aligning a beam of the multiple measuring beams with the receiver.7. The laser scanner according to claim 1, wherein: the transmittercomprises multiple laser diodes arranged on a carrier; the carrier hasat least two different flexure states; and based on different flexurestates in each case the laser diodes generate different multi-beam scanpatterns of the at least two multi-beam scan patterns.
 8. The laserscanner according to claim 1, wherein: the transmitter comprises one ormultiple radiation sources; the transmitter comprises a holographicstructure and is configured for generating a first and a second group ofbeams based on the holographic structure; and the transmitter and thecomputing unit are configured such that one multi-beam scan pattern ofthe at least two multi-beam scan patterns is based on the first group ofbeams and another multi-beam scan pattern of the at least two multi-beamscan patterns is based on the second group of beams.
 9. The laserscanner according to claim 8, wherein: the first group of beams isgenerated based on a first radiation source; and the second group ofbeams is generated based on a second radiation source.
 10. The laserscanner according to claim 8, wherein: the first group of beams isgenerated based on a first radiation source; the second group of beamsis generated based on a second radiation source; the receiver comprisesan objective lens; the transmitter comprises the first and the secondradiation source; the transmitter is configured to generate the firstgroup of beams based on the first radiation source and to generate thesecond group of beams based on the second radiation source; and theholographic structure is configured such that the beams of the first andthe second group of beams emanate from the objective lens.
 11. The laserscanner according to claim 1, wherein: the receiver comprises anopto-electronical sensor based on an arrangement of a multitude ofmicrocells; the sensor is configured as an array of single photonavalanche photodiodes; the sensor is configured such that the microcellscan be read out individually or in groups of microcells, such thatsub-areas of the receiver are settable to be read out separately; thereceiver and the computing unit are configured such that differentsub-areas of the receiver are set by the computing unit; and wherein themultiple measuring beams have different measuring beams, whereinreturning parts of different measuring beams of the multiple measuringbeams in each case are read out by different sub-areas of the receiver.12. The laser scanner according to claim 11, wherein: the receivercomprises multiple opto-electronical sensors, including multiple arraysof single photon avalanche photodiodes; and the multiple sensors arearranged in a one-dimensional, two-dimensional, or three-dimensionalmanner, each sensor having separate control and/or evaluationelectronics.
 13. The laser scanner according to claim 1, wherein: thelaser scanner comprises a customizable component, the customizablecomponent comprising an optically active element formed by at least oneof: a customizable emitter array, including a VCSEL or a VECSEL array,configured to form a customizable emitting component for generating atleast one beam of the multiple measuring beams; and a customizablereceiving array, configured to form a customizable receiving componentfor detecting returning parts of the multiple measuring beams.
 14. Thelaser scanner according to claim 13, wherein: the laser scannercomprises a plurality of the customizable components; and eachcustomizable component is configurable by software such thatcustomizable components are grouped to at least one common receivingcomponent and/or to at least one common emitting component.
 15. Thelaser scanner according to claim 1, wherein: the laser scanner isconfigured to provide simultaneous scanning with a first and a secondmulti-beam scan pattern of the at least two multi-beam scan patterns;and the repetition rate for deriving distance measuring data based onthe first scan pattern is different from the repetition rate forderiving distance measuring data based on the second scan pattern. 16.The laser scanner according to claim 15 wherein: the first scan patternprovides a set of diverging beams of a first wavelength; and the secondscan pattern provides a set of beams of a second wavelength, said secondwavelength being different from the first wavelength.